Effect of temperature gradient on thick film selective emitter emittance

. A ,temperature gradient across a thick (♢ .1 mm) film selective emitter will produce a significant reduction in the spectral emittance,from the notemperature,gradient case. Thick film selective emitters of rare ,earth doped host materials such as yttrium-aluminum-garnet (YAG) are examples where temperature gradient effects are important. In this paper a model ,is developed for the spectral emittance assuming ,a linear temperature gradient across the film. Results of the model indicate that temperature gradients will result in reductions the order of 20% or more in the spectral emittance.